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Omega-3s and Prostate Cancer Fact Check: What’s a Guy to Do?

The media is abuzz in the wake of a surprising new study published in the Journal of the National Cancer Institute linking omega-3s to a higher risk of prostate cancer. But should men give up eating their salmon?

Omega-3 polyunsaturated fatty acids are generally acclaimed for their link to reduced inflammation and overall health promotion, especially heart health. Omega-3s are found in salmon and other fatty fish as well as in supplements. Fish oil capsules containing the omega-3s EPA and DHA are among the most popular supplements.

The study measured the percent of three omega-3s most commonly found in fish and supplements – DHA, EPA and DPA – in the blood of 834 men with prostate cancer matched to 1,393 men without cancer. Men with the highest percentage of omega-3s in their blood had a 43% increased risk of prostate cancer compared to those with the lowest concentration. No increase in risk was found in the men in the two middle quartiles – in other words, those with moderate levels.

What’s a guy to do? For now, follow AICR’s evidence-based recommendations for prostate cancer. Men can include plenty of foods rich in the antioxidants lycopene (tomatoes are a great source) and selenium (found in sunflower seeds and Brazil nuts) and rest easy knowing they’re helping reduce their risk of not only cancer but other chronic diseases. What about fish? “Men should not fear eating fatty fish in moderation – that’s to say, a couple servings per week,” says Karen Collins MS, RDN, CDN and nutrition advisor to AICR.

Flaxseed, a source of a different type of omega-3 is not linked with risk in this study, and is also a healthy choice.

The current study raises more questions than it provides answers. For one, the study cannot conclude whether the high blood levels of omega-3s were from supplements. The men were not asked about their dietary intake of fish or dietary supplements, nor were they asked about physical activity or other lifestyle factors that may have affected cancer risk.

Collins also called attention to the fact that “in all groups, half the men had smoked and about 80% were overweight or obese. We know nothing of their diet or their use of fish oil supplements. It’s highly unlikely these American men were eating salmon every night…. Relying on omega-3 supplements is just not enough in the context of an overall unhealthy lifestyle.”

We need further research on this question, including a closer look at diet. this study was an observational study; it can only identify things that may be linked to each other and can’t show cause and effect. The authors put the call out for further research to help us understand the possible mechanisms behind their findings. (Although this study confirms earlier work by the same group of researchers, the authors do not have an explanation for the association.)

AICR’s Continuous Update Project will incorporate these findings into its growing evidence base as it keeps the science current on links between cancer risk and diet.

In the meantime, AICR does not recommend relying on dietary supplements of any kind for cancer prevention. Getting the nourishment you need, including omega-3s, is best done through food, not pills or capsules. So for now, put your dollars toward some tasty whole-food finds at the farmer’s market or fish market instead of on a pricey bottle of omega-3 supplements as we wait to learn more.

Arissa Anderson is an MPH/RD candidate from the University of Minnesota School of Public Health and dietetic intern with the American Institute for Cancer Research. Connect with Arissa on Twitter @ArissaAnderson.